Plaster cutter



Aug. 18, 1936.

G. M. cHRlsfnANsoN PLASTER CUTTER 2 sheets-sheet 1 Filed Janl. 18, 1935Aug. 18, 1936. G. M. cHRlsTlANsoN 5 2,051,199

PLASTER CUTTER l Filed Jan. 18, 1935 2 sheets-sheet 2 Fb'g. 1%

C KYENTOR AORNEY Patented Aug. 18, 1936 UNITED STATES PATENT OFFICEPLASTER CUTTER George M. Christianson, Union City, N. J. ApplicationJanuary 18, 1935, Serial No. 2,3775

13,Clams. (Cl. 'i2-138) This invention relates to plaster cutters, suchas may be used by plasterers and painters when repairing defectiveplastered ceiling or side walls by cutting out and removing portionsthereof, or by opening existing cracks in the plaster sufliciently sothat fresh plaster may be applied and levelled oi to produce acontinuous smooth surface.

An object of the invention is to provide a tool which is especiallyadapted for the purpose stated, and which will perform its workexpeditiously and economically.

Another object of the invention is to provide a tool Whose cutting blademay be maintained in proper Working condition without the use of agrinder or the like.

A further object of the invention will be found in the improvedorganization of the blade and its handle so that the tool, as a Whole,may be folded to be carried in aY pocket, or the blade may be openedangularly to the handle or into extended alignment therewith, the bladeand handle becoming securely locked relatively to each other, in eitherof the conditions named.

Another object of the invention is the provision o f a blade whoselength is divided by grooves into a series of connected sections. whichmay be consecutively brokenoif with a pair of pliers or the like, topresent a new cutting edge or point when required.

Other objects and advantages of the invention will hereinafter appear. g

In general practice, when repairs in plaster are to be made, requiringeither the removal of patches of plaster, or else the opening orenlargement of existing cracks, the Workmen are apt to use what isgenerally called the broad knife for breaking through the plaster, thisprocess, however, rendering the broad knife unfit for the use for whichit was orginally intended, and therefore it needed resharpening to bringit back into usable condition.

'I'he tool of the present invention has, therefore, been designed forits particular purpose and for its ready and easy reconditioningWhenever the cutting edge or the point of the blade becomes dull oruni-lt for further use.

In the accompanying drawings- Figure 1 shows my improved cutter, withits blade extending substantially atV a vright angle to the holder orhandle.

Fig. 2 is a top edge View thereof.

Fig. 3 is a side view of the cutter` shown in Fig. 1. i f

Fig. 4 is an enlarged section taken on line 4-4 of Fig. 1.

Fig. 5 is a similar view, taken on line 5 5 of Fig. 1.

Figs. 6, 7 and 8 illustrate the front views of 5 the handle, bladeholder and the blade respectively. Y

Fig. 9 is an obverse perspective view of the blade, per se.

Fig. 10 illustrates the tool as it appears when 10 folded to b e carriedin a pocket.

Figs. 11 through 18 show a modication in the construction of the tool,which, in these figures, is represented as a power-driven device insteadof a hand-tool as shown in the preceding figures. l5 Here, Fig. 11 showsthe face view of a multiblade cutter; Fig. 12 is a central verticalsection thereof; Fig. 13 represents an edge view of the cutter shown inFig. 11; Fig. 1li is a cross-section of the blade holder and the bladelocked therein, on 20 line M-M'of Fig. 11. Figs. 15a, 15b are sectionson line |5| 5 of Fig. 11-Fig. 15a showing the blade free to slide, whilein Fig. 15b Vthe blade is clamped in place.

Fig. 16 is a perspective Vview of the blade, per se. 25

Fig. 17 shows a fraction Vof the disk, bladeholder and theclamping-plate ready to be placed thereinto, and Y Y Fig. 18 representsthe clamping plate in operative position.

Referring first to the embodiment of the invention shown in Figs. 1 to10 inclusive, my improved cutter comprises a handle 20 consistingpreferably of a sheet-metal plate 2| which is stiffened by a Wood handgripr22 riveted thereto, as 35 at 23. At its upper end the plate 2| hasattached to it one end of a blade holder 24, the connection beingestablished by a bolt 25 (see Fig. 4) which is provided with a squareshoulder 26 adapted to fit square perforations 21, 28 provided thereforin v4.0 the handle plate 2| and the blade holder 24, respectively. Henceit will be seen that the blade holder'24 may assume four differentpositions relative to the handle 20, viz. as shown in Fig. 1 (extendingto the right at a right angle therefrom) or vextending to the lefttherefrom, or beyond the handle V(in a straight line therewith) or inline with and covering the body of the handle, as shown in Fig. 10. ItwillY also be understood that, when the handle and blade holder are inany of the positions named, and a nut 25 is tightened, the handle andblade holder become immovably locked together in those positions,therefore making the device a stiff and strong structure. f Y"VVExperience has demonstrated that the working-end of the cutter bladeis best adapted for its work when'it is shaped kas illustrated in Figs.l, 8 and 9 in which the blade 29 is shown made'o-f thin Vsheet steeladapted to be slid into desiredY posi-V tion'in the holderr24, thelatter being also made of sheet metal, having its longitudinal edgesbent tojormV channels 24a (see Fig. 5) whose margins overlap'the edgesofthe blade and are sufficiently spaced from the mainplate ofthe holderto also overlap'thefopposite upper and lower) edges of a'clampngV plate30.

It should be understood that both the blade Y.zey

as well 'as the clamping plate V3l) are normally freely andindependently slidable in the -channels* 24a of the holderthe blade 29preferably having Y at its inner enda'bent-up tabl3| which projectsoutwardly Yenough to serve as .afin'ger hold, while the clampingplate30'has Va binder-.screw ,32,`

which projects beyond the holder and serves as a ngerfpiece `forY movingthe clamping plate into Vthe desired position. When, now, the screw 321sbeing turned in ,theV plate k30 until its end Aabuts against the face ofthe blade, the clamping plate 30 will ,perforce be 'pulled outwardlyuntil its upper and lower edges bringup against the inside Vfaces of thechannel lips 2412 (see Fig. 5) andthe screw 32 therefore serves forVholding both the blade2a as well as the clamp-plate 3| Vin xedpositions in the holder 24,.k Y

. As above stated one featureof the present invention is the improvedform of thecutter blade which is so'constructed that When either thecut- Y blade and the clamping plate may 1550 ting edge or the pointbecomes dull orrbroken, the

VYdamaged portion of the blade may be broken off,

blade a'thin and leaving on the main body of the be used .roughly,ragged cutting edge which may on the plaster or the like withoutlosjngits` eilici-v 'ency as a cutter.

YIn order to accomplish'this result, my improved blade isdiagonally-grooved,across its face, as at 35, either by milling orindentne; and thus dividingthe'blade-length into a series of similarcon- Y nected sections 36, which may be broken off or` 4severed fromeach `other at the grooves :ii-leaving a sharpragged edge 31 and anacutely angular 'and correspondingly-sharp point 3B, asleft by theVdiagonal break--it being understood that the `be relocated in anydesired position inthe holderto again form a, ,rigidY structure.

When not in use,'andtoadapt the tooltorbe carriedv :in a pocket,

. Y thelblademsy be slipped not project vbeyond the holder and thelatter may be alenedgwiththe handle,

' `as above described, thus'leafving no sharp edges i Vorprojectionswhich mighttear the pocket.

The tool thus .far described answers the purpose of a hand tool `adaptedfor use on smaller jobs, `and, where minorrepairs are to be made, ForVlarger jobs. which require cutting out larger areas of plaster, I Dreiertousea power drivencutting device, suchas is incidentally Vshown inFlgsfll to 19, inclusive.V

Inthat case, I deem,.it expedient to provide a; plurality of cutters,vtheV blades 40 of Y' which are held for indivdualfadiustment and Ytreatmentv `in holdersllI'-'eigl1tV being shownriveted, individuallyorin a multiple unit Aon a disk 42. the central portionof-vvhich hasajhub'42a which may besecured to the driving spindle 43 jbya set screwy.4.4.

Inasmuch as the cuttingdevice as ai whole isY inthe present instancearpower driven device,

hand, Iprovide a handle 45 which is preferably v made of wood but has ametallic bushing 46 serving as a bearing for the spindle 43. At itsother end the spindle may be connected to a motor, either directly orthrough the intervention of a ilexible shaft (not shown) the latterconstruction being preferable on account'ofits lightness inv Weight andease ofV hand-manipulation. The disk and its cutters partake of thenature of a'circular saw, whose teeth (cutters)V are ad-V justableradially, the individual blades V4l) being grooved or lscoredin Vthesame manner as the blades 3l previously describedj but, inasmuch as ,thepresent device is power driven at a high speed,

' I deem it expedient to provide means whereby the Vblades will belocked against outward radial slip movement which might be caused bycentrifugal force due to the high velocity of the disk. I pro- 'videthese means ina very simple manner, pref-` erably by forming at theinner end of each bladeV a projection or bent-up tab 46 whose sides 4l(see Figs. 1,4 and 17) are tapered'and of .such size that the tab-widthat its bottom or lroot 48 isless than the width of the space between theholderVV Y lips 49'; Therefore, when the tab 46 gis grasped by thefingers and raised until the edges ofthe longitudinally in its holderwithout hindrance. On the other handwhen the tab 46 is in a position ofalignmentwith any-one setof notches 50 (see Fig. 18) provided'in theholder lips 49, vand then released, the Vtapered sides 41 of the tabwill enterthose notches until theyibecome interlocked and wedged inplace therein, Vthe tightness of this wedging eiect depending, ofcourse,upon the action of the clamp plate 5l and binder screw 52 (see Fig. 15b)whose functions and construction are identical with thosepreviously-designated by 3U and 32, respectively,.the interlock betweenblade and holder being effective in both directions longitudinallyof theholder.

Inasmuch as it isessential to maintainthe radial distances ofthe pointsof al1 bladesfrom the axial center of the disk'the samein order that thepoints may all be equally eliectiveduring the operation of the tool,several features are'incorporated in my improved device, viz., allholders lare notched alike, the distances between thesevveral grooves ofVthe blades, so that the several connected sections of the latterare'also allalike,

' and,When the pointed end-sectionof anyone blade of the series isremoved or Vbroken off, it is only necessary to move that, particularblade4 radially outward in its holder *until the tab 46Y enters the nextoutward set of notches 50 in the the rst Vand nearest grooveV 35 of eachblade notches, and the distance between the tab 46 and'V being also thesame in all cases; (3) While I pre'- fer to spacethe eight holdersillustrated at equal angles (45) on the disk, such Vequal distributionis not essential, provided, howeven'thatthe opposite pairs should be indiametral alignment in order to facilitate the balancing of the deviceto minimize its vibration under high speed.

Y upper face of the blade engage theunderside of K 'Y the holderlips'49, the blade can 'be slid alongV VFrom the foregoing description,it will be 75,

derstood that a power driven tool constructed in accordance with thepresent invention is capable of doing its work rapidly and cleanly, andthat it may be guided to cut along definite lines, leaving the edgesclean-cut so that new plaster may be matched in place evenly andsmoothly. In order to guide the cutter properly, it is, of course,essential that the cutting operation of the tool be performed Withoutundue or excessive vibration, such as may be caused, for instance, whenblades of different lengths are used and will naturally throw the diskout of balance. However, this fault may be remedied by the fact that theclamping plates With their binder-screw may be adjusted longitudinallyin the holders to counterbalanoe each other at opposite sides of thedisk center, and therefore minimize, if not entirely eliminate, thevibration, thus providing a smoothrunning and non-trembling device.

Variations and modications may be made within the scope of thisinvention and portions of the improvements may be used Without others.

Having thus described the invention, what is claimed as new and forwhich it is desired to obtain Letters Patent, is:-

1. A cutting tool comprising a blade having grooves in its surfaceextended across the blade to form a series of connected sections adaptedto be broken 01T along the groove lines, substantially as and for thepurpose described.

2. A cutting tool comprising a blade having diagonal grooves across itsface forming a series of connected sections adapted to be severed fromeach other at the groove lines and leaving at its severing line adiagonal cutting edge, and an acute-angle cutting-point on one of thesections.

3. A cutting tool comprising a holder having channels at its oppositeedges, a blade slidably supported in the channels of said holder, aclamping plate also slidably held in said channels, and a binder screwcarried by said plate and extending outside of said channels for I'lrstsliding said plate into proper position in the channels and subsequentlyclamping said plate, blade and the holder together and in xed positionstherein.v

4. A cutting tool comprising a blade, a holder slidably receiving saidblade, said blade being shiftable in said holder in a direction at anangle to the direction of sliding of the blade, means carried by saidblade and engaging said holder for locking said blade against slidingmovement in the holder, and means for then locking said blade in theholder against such shifting.

5. A cutting tool comprising a holder having spaced notches and a bladehaving a projection adapted to enter any of said notches to lock thesame against movement relative to each other, said blade having groovessimilarly spaced in its surface and forming connected sections adaptedto be severed at the groove lines to present a new cutting edge andpoint. 4

6. A cutting tool comprising a holder having its longitudinal edges bentto form a pair of opposite channels, one of the channel-walls having aseries of equally spaced notches, a cutter-blade adapted to be movedlongitudinally in said channels and having a tab adapted to enter anyone of said notches and to be locked therein, and a device for holdingsaid tab in said notch.

7. A cutting tool comprising a holder having its longitudinal edges bentto form a pair of opposite channels, one of the channel-Walls having aseries of equally spaced notches, a cutter-blade adapted to be movedlongitudinally in said channels and having a tab adapted to enter anyone of said notches and to be locked therein, said blade also havingequally-spaced grooves in its surface to form a series of equalsections, the central distances of said grooves being equal to thecentral distances of said notches, and a device for holding said tab insaid notch.

8. A cutting tool comprising a handle, a bladeholder attachable thereto,means for positioning and locking said blade-holder on the handle, ablade slidable in said holder, and a device for locking said blade inposition in the holder.

9. A cutting tool comprising a blade having V- shaped diagonal groovesacross its face forming a series of connected sections the terminal oneof which is adapted to be severed from an adjoining section at the linebetween these two sections to remove the terminal section by splittingthe blade material along said line opposite the apex of the V thereby toleave said adjoining Section with a cutting edge having a bevelestablished by a leg of the V, said edge terminating in an acute anglecutting point.

10. A cutting tool comprising a blade having V-shaped grooves in itssurfaceV to form connected sections the terminal one of which is adaptedto be broken oi along one of the groove lines, to leave at thebreaking-off line a cutting edge following substantially said grooveline and being rough and irregular because established by the breakingof the blade material opposite the point of the V of said line, saidedge having a bevel established by a leg of the V.

l1. A cutting tool comprising an elongated iiat blade having diagonalgrooves across its face forming a series of connected sections adaptedto be severed from each other at the grooves, and leaving at itssevering line a diagonal cutting edge and an acute angle cutting pointon one of the sections; a holder for the blade having its longitudinaledges bent toform a pair of opposite channels in which said blade isslidably mounted and having its edge diagonal so as to be parallel withthe diagonal grooves of said blade; and means for securing the blade inthe holder against casual movement.

12. A cutting tool comprising an elongated iiat blade having aiinger-piece at one end; a holder for the blade having its longitudinaledges bent to form a pair of opposite channels in which said blade isslidably mounted with the finger-piece in the blade projected throughthe space between said longitudinal edges for manual engagement toadjust the blade relative to the holder; and means for securing theblade in the holder against casual movement.

13. A cutting tool comprising an elongated flat blade having afinger-piece at one end; a holder for the blade having its longitudinaledges bent to form a pair of opposite channels in which said blade isslidably mounted with the finger-piece in the blade projecting throughthe space between said longitudinal edges for manual engagement toadjust the blade relative to the holder; a clamping plate having itslateral edges located in said opposite channels and slidable thereinrelative to the blade and holder; and means on the clamping plate forsecuring the blade in the holder against casual movement.

GEORGE M. CHRISTIAN SON.

